The present invention relates to a control element for selectively establishing electrical contacts. In particular, the present invention concerns a four-way rocker, preferably for use in car radios.
In the case of electronic devices that have small user interfaces, such as car radios and other consumer electronic equipment, the numerous functions need to be controlled by compact control elements that combine a variety of electrical switching functions in a single unit. Despite their compact design, control elements of this type need to be constructed so that multiple electrical contacts are not inadvertently closed simultaneously during operation, causing the device to operate in an uncontrolled manner.
In addition, a control element of this type must last a long time. The target is a service life covering several hundred thousand actuations per switch position. The control element haptic properties, i.e., the force and distance traveled to trigger an electrical contact, must meet defined standards to convey a reliable switching sensation to the user.
Control elements of this type in the form of pushbutton switches are known in the related art, for example the element described in German Patent No. 195 35 423. The pushbutton switches described in this publication have a depression in their underside that rests on a round seating.
Pressure applied to one side by the user causes the pushbutton switch to tilt and activate momentary-contact switches arranged around the round seating. Retaining ribs between the individual momentary-contact switches guide the tilting motion of the pushbutton switch and ensure that only one momentary-contact switch can be triggered at a time. The momentary-contact switches are mounted on a p.c. board that is connected to the device electronics.
However, this control element has the following disadvantages: due to the location of the pushbutton switch acting from above upon the momentary-contact switches mounted on the p.c. board, the control element must be mounted at a great overall depth, in particular because the tilting motion of the pushbutton switch must first be guided in the appropriate direction by the retaining ribs before it can actuate one of the momentary-contact switches. When more than two momentary-contact switches are used, the retaining ribs also frequently prevent any electrical contact from being established at all, with the pushbutton switch merely bumping into the retaining ribs instead. Finally, the electromechanical momentary-contact switches have a considerably limited service life, which limits the life of the overall pushbutton switch.
The control element according to the present invention for selectively establishing electrical contacts has the advantage that the use of a contact mat which structurally separates the resetting elements from the contact elements enables both of these components to be independently optimized for their own specific applications. The resetting elements, which are provided on the contact mat and return the switch grip to the neutral position after selectively establishing an electrical contact, provide a reliable switching sensation during operation. The contact elements, which are also provided on the contact mat, are operated largely without force and are designed for several hundred thousand switching cycles. The one or more assigned resetting elements protect them against excessive mechanical load.
By replacing the momentary-contact switches with a contact mat that interacts directly with the p.c. board, the control element can have a very flat overall shape, thus saving space. A further advantage of using a contact mat is that it has a long service life, ensuring that the overall control element will also last a long time. The small number of individual parts in the control element also enables the component to be assembled easily and therefore economically.
According to one preferred embodiment, the contact mat is made of an elastic material, such as silicone, which retains the necessary flexibility even after many switching operations. The control element grip preferably includes a rocker on the side facing the user, behind which is provided a contact frame which transmits the movements of the rocker to the contact mat. To apply a uniform resetting force to the contact frame, each contact element is preferably surrounded on the contact mat by preferably two resetting elements which return the contact frame, and thus the rocker, to the initial position. The resetting elements are preferably formed by raised areas on the contact mat, referred to as contact domes, which are pressed together flexibly by the contact frame.
The rocker is preferably mounted so that it tilts in total of four directions. However, it is also possible to provide correspondingly more tilting directions. Four contact elements, which operate in the different directions during tilting, are preferably correspondingly provided on the contact mat.